Abstract 5944: <i>Euglena</i> water extract attenuates lung tumorigenesis induced by tobacco-specific carcinogen through modulation of gut microbiota metabolites
Authors: Deepa Upreti, Susumu Ishiguro, Ayaka Nakashima, Kengo Suzuki, Jeffrey Comer, Masaaki Tamura
Journal: Cancer Research (2022)

Abstract Lung cancer is the leading cause of cancer-related mortality in the world. Our previous studies have shown that the oral administration of Euglena water extract significantly inhibits the growth of grafted lung carcinoma tumors in mice. Euglena gracilis, a single-celled alga used as a nutritional dietary supplement, possesses a broad range of medicinal properties including anticancer activity against a few types of cancers. Most studies describing this anticancer activity have used xenograft cancer mouse models, but not carcinogen-induced cancer models. Since tobacco smoke carcinogen-induced lung carcinoma in mice mimics human lung cancer development, in this study, we investigated the anti-cancer properties and the underlying mechanism of the E. gracilis water extract against lung tumorigenesis induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). A/J mice (n=10 per treatment group) were used and the treatment regimen consisted of: (i) PBS control, (ii) Euglena water extract 2 weeks before NNK injection (pre-NNK) and (iii) this extract 10 weeks after NNK injection (post-NNK). We examined the metabolite landscape of the gut microbiota by a high-throughput metabolomics approach. The Euglena water extract treatment greatly attenuated NNK-induced tumorigenesis in lungs of A/J mice. A Partial Least-Squares Discriminant Analysis demonstrated a separation of the fecal metabolites between the control and treatment groups. Using the untargeted metabolomics, we identified 20 potential metabolites that were differentially expressed in the Euglena extract (pre- and post-NNK) treatment groups as compared to the control group. Specifically, succinate, malate, triethanolamine, acetylserine were increased with the Euglena water extract treatment in comparison to the control. These metabolites are involved in the biosynthesis of short-chain fatty acids (SCFA). Furthermore, using the targeted analysis of SCFA, we observed a significant increase in acetic acid in the feces of mice treated with Euglena water extract both before and after NNK exposure; however, butyric and propionic acids were significantly higher in only post-treated mice. Moreover, in vitro treatment of both human and murine lung cancer cells with SCFA significantly suppressed their proliferation. The present study indicated that treating with the Euglena water extract both pre- and post-NNK exposure greatly inhibits NNK-induced lung tumorigenesis in mice even after early tumorigenesis has been established. This study also found that Euglena water extract increases the levels of SCFA and their precursors in the feces of the treated mice indicating a role of gut microbiota in suppressing the NNK-induced tumorigenesis. This study was supported by 2017 EUGLENA-RC2 (MT and JC), Kansas State University Johnson Cancer Research Center (MT and JC), and NIH grant P20 GM103418 (MT). Citation Format: Deepa Upreti, Susumu Ishiguro, Ayaka Nakashima, Kengo Suzuki, Jeffrey Comer, Masaaki Tamura. Euglena water extract attenuates lung tumorigenesis induced by tobacco-specific carcinogen through modulation of gut microbiota metabolites [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5944.